Null Pointer Exception error while creating array of files

Question

Inside the for loop, depending on if condition, files need to be created every time. While executing the code, NullPointerException pops up.

    File[] tempDir=null; 
    for(  )
    {
    if(condition){
        try {
            tempDir[l]=new File(tempFileName);
            if(l==0){
                tempDir[l++].mkdir();
                /*code*/
            }
            if (!tempDir[l].exists()){
                tempDir[l++].mkdir();
                /*code*/
            }
        }
    }

Answer 1

You don't initialize the tempDir array.

Change

File[] tempDir=null; 

to

File[] tempDir=new File[somePositiveInteger]; 

tempDir[l] would throw a NullPointerException if tempDir is null.

Answer 2

You are initializing your File array to null here ,

File[] tempDir=null;

So you are getting NPE when you are trying to find the first element of the File Array here ,

tempDir[l]=new File(tempFileName); // tempDir[l] represents the element at position 1

So you should declare the size of the array withe positive value as Eran pointed out in his answer . Also have a look at How to initialize an array in Java?